Experimental and theoretical studies of emodin interacting with a lipid bilayer of DMPC

Emodin is one of the most abundant anthraquinone derivatives found in nature. It is the active principle of some traditional herbal medicines with known biological activities. In this work, we combined experimental and theoretical studies to reveal information about location, orientation, interaction and perturbing effects of Emodin on lipid bilayers, where we have taken into account the neutral form of the Emodin (EMH) and its anionic/deprotonated form (EM^?). Using both UV/Visible spectrophotometric techniques and molecular dynamics (MD) simulations, we showed that both EMH and EM^? are located in a lipid membrane. Additionally, using MD simulations, we revealed that both forms of Emodin are very close to glycerol groups of the lipid molecules, with the EMH inserted more deeply into the bilayer and more disoriented relative to the normal of the membrane when compared with the EM^?, which is more exposed to interfacial water. Analysis of several structural properties of acyl chains of the lipids in a hydrated pure DMPC bilayer and in the presence of Emodin revealed that both EMH and EM^? affect the lipid bilayer, resulting in a remarkable disorder of the bilayer in the vicinity of the Emodin. However, the disorder caused by EMH is weaker than that caused by EM^?. Our results suggest that these disorders caused by Emodin might lead to distinct effects on lipid bilayers including its disruption which are reported in the literature.     

Time-Resolved Fluorescence in Lipid Bilayers: Selected Applications and Advantages over Steady State

Fluorescence methods are versatile tools for obtaining dynamic and topological information about biomembranes because the molecular interactions taking place in lipid membranes frequently occur on the same timescale as fluorescence emission. The fluorescence intensity decay, in particular, is a powerful reporter of the molecular environment of a fluorophore. The fluorescence lifetime can be sensitive to the local polarity, hydration, viscosity, and/or presence of fluorescence quenchers/energy acceptors within several nanometers of the vicinity of a fluorophore. Illustrative examples of how time-resolved fluorescence measurements can provide more valuable and detailed information about a system than the time-integrated (steady-state) approach will be presented in this review: 1), determination of membrane polarity and mobility using time-dependent spectral shifts; 2), identification of submicroscopic domains by fluorescence lifetime imaging microscopy; 3), elucidation of membrane leakage mechanisms from dye self-quenching assays; and 4), evaluation of nanodomain sizes by time-resolved Förster resonance energy transfer measurements.     

Acoustic interactions between free-living mother–calf Antillean manatees,Trichechus manatus manatus

Journal of Ethology - Acoustic signalling plays a crucial role in mother–calf communication. Here, we describe the acoustic signalling of three free-living Antillean manatee mother and calf...     

Impacts of leafroll‐associated viruses (GLRaV‐1 and ‐3) on the physiology of the Portuguese grapevine cultivar ‘Touriga Nacional’ growing under field conditions

The impact of mixed infection of grapevine leafroll‐associated virus 1 and 3 (GLRaV‐1&‐3) on physiological performance of the Portuguese grapevine variety ‘Touriga Nacional’ was evaluated during 3 years with the main purpose of understanding the drastic reduction in yield. Overall, gas exchange was negatively affected in leaves with these leafroll virus infections. Particularly at ripeness stage, the reduction in stomatal conductance (g_s) was higher than in net CO₂ assimilation rate (A), leading to higher intrinsic water use efficiency (A/g_s) in infected leaves. However, the decrease in g_s and A were not a consequence of the decrease in bulk water potential, as the water index/normalised difference vegetation index ratio suggested similar magnitude for both treatments. The maximum quantum efficiency of photosystem II was unaffected by GLRaV‐1&‐3, whereas quantum effective efficiency of PSII, apparent electron transport rate and photochemical quenching significantly decreased in infected leaves and these was paralleled by a significant increase of non‐photochemical quenching. Relative to carbon metabolism, the analyses of the net CO₂ assimilation rate/photosynthetic photon flux density (A/PPFD) and net CO₂ assimilation rate/internal CO₂ concentration (A/C_i) curves revealed that virus infection had a negative effect on light saturated rate of CO₂ fixation at high irradiances and carboxylation efficiency but, in contrast, apparent quantum yield of CO₂ fixation was significantly higher. Meanwhile, the presence of GLRaV‐1&‐3 resulted in a marked decrease in photosynthetic pigments, soluble sugars and soluble proteins contents, while starch and anthocyanins were significantly improved. N, P, Ca, S and Fe leaf concentrations significantly decreased, while K, Mg, B, Cu, Zn and Mn were unaffected by these two leafroll virus species. Infected plants showed a significant decrease in yield, mainly due to a lower cluster weight. These results emphasised the important role of GLRaV‐1&‐3 as a biotic stress for the grapevine physiology and consequently to yield attributes.     

Synthesis and binary QSAR study of antitubercular quinolylhydrazides

In continuation with our previous work in anti-TB research area, in the present study we have demonstrated the structural diversity of quinolylhydrazides as potent anti-tuberculars. The compound library was synthesized by molecular hybridization approach and tested in vitro against Mycobacterium tuberculosis H₃₇Rv strains. Among the designed conjugates, the most promising molecules were found to exhibit 100% Growth Inhibition (GI) at MIC <6.25 μg/mL. Moreover, several analogs in the designed series were also turned out as excellent anti-tuberculars. To probe the structural characteristics influencing on the SAR, the classification model was generated using a binary QSAR approach termed recursive partitioning (RP) analysis. The significant features outlined by the RP model act as a guide in order to design the ‘lead’ compound.     

Modelling the climate suitability of green carpenter bee (Xylocopa aerata) and its nesting hosts under current and future scenarios to guide conservation efforts

Due to local extinction, the endangered green carpenter bee (Xylocopa aerata) has a disjunct distribution in the southeast of Australia. The species relies on dead softwood from a small selection of plant species for making its nests. Habitat fragmentation, combined with deleterious fire events, is thought to have negatively impacted on nesting substrate availability and recolonisation chances. Here, we use MaxEnt algorithm to model both the current distribution and the effect of climate change scenarios on the distribution of both X. aerata and four plant species that provide most of its nesting substrate: Banksia integrifolia, B. marginata, Xanthorrhoea arborea and Xanthorrhoea semiplana subsp. tateana. The annual mean temperature is the strongest climatic predictor of the distribution of X. aerata and its host plants. The modelled distribution of the bee under current climatic conditions indicates that climatic factors are unlikely to cause local extinctions. In all future scenarios, suitable areas for X. aerata and each of its nesting hosts are expected to contract towards the southeast of mainland Australia. The suitability of Kangaroo Island for the bee and its current local current host species is maintained in all scenarios, while Tasmania will become increasingly suitable for all species. The Grampians National Park in western Victoria, where the bee species were last seen outside of its current range (in the 1930s), is predicted to remain suitable for X. aerata and several host plants under all scenarios. Therefore, this relatively large area of native vegetation may be a good case study for re‐introduction as part of future conservation efforts.     

Experimental canine mucocutaneous leishmaniasis (Leishmania braziliensis braziliensis)

Four mongrel dogs were intradermically inoculated with 3 x 10(6) Leishmania braziliensis braziliensis promastigotes. Three out of the four animals developed cutaneous lesions respectively 4, 7, and 8 months after. The fourth dog did not develop lesion at the inoculation site, but a mucosal ulcer was seen 16 months after the inoculum. Clinical, histopathological, and serological findings were similar to what is found in natural canine infection as well as in the human disease. These results suggest that dogs may be an useful model for L. b. braziliensis infection.     

A human breast tumor cell line (BT-474) that supports mouse mammary tumor virus replication.

A human breast tumor cell line BT-474 derived from an invasive ductal carcinoma was experimentally infected in vitro with a mouse mammary tumor virus from the TIII strain (RIII-MuMTV). The virus that replicated in the human cells was characterized as a mouse virus by immunofluorescence, electron microscopy and the presence of a specific RNA-directed DNA polymerase. The cells themselves were human as per the karyotype and isoenzyme migration patterns. It is concluded that human cells are susceptible to the mouse mammary tumor virus and can, eventually, support its replication.